Block copolymer electrolytes containing polymeric additives

ABSTRACT

Polymer electrolytes incorporating PS-PEO block copolymers, PXE additives, and lithium salts provide improved physical properties relative to PS-PEO block copolymers and lithium salt alone, and thus provide improved battery performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 15/275,308, filed Sep. 23, 2016, which, in turn, claimspriority to U.S. Provisional Patent Application 62/235,499, filed Sep.30, 2015, both of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to electrolytes for lithium batteries,and, more specifically, to additives for solid block copolymerelectrolytes.

Some block copolymer electrolytes include a “soft” block that providesionic conductivity and a “hard” block that provides structuralintegrity. The resilience of polymer electrolytes based on such blockcopolymers is dependent on the thermomechanical properties of theso-called “hard” or “mechanical” block. Sufficient physical resistanceto the intrusion of uneven or dendritic lithium growth when in contactwith lithium metal electrodes is necessary to prevent penetration oflithium through the electrolyte and shorting of the cell. Some currentblock copolymer electrolytes use polyethylene oxide for the soft blockand polystyrene for the hard block. Polystyrene is a well-characterized,inexpensive polymer with good properties, such as a high glasstransition temperature (Tg, ˜100° C.), that allow it to be used atfairly high temperatures while maintaining high modulus values (>1 GPa),and good physical resiliency. Further improvements in either of theseproperties would be expected to increase battery performance byproviding even greater physical resistance to lithium intrusion and byallowing operation at even higher temperatures, which would increase theionic conductivity of the soft block.

There are a number of polymers that have better high-temperatureproperties than polystyrene and might be considered for use as the hardblock in block copolymer electrolytes. But many of these are expensiveengineering thermoplastics that may be difficult or impossible to usefor forming block copolymers with poly (ethylene oxide) and/or todissolve and process as a solution.

Another approach would be to crosslink the polymer used for the hardblock. Cross-linking can improve physical properties but requires greatcare in processing and perhaps additional processing steps forcharacterization and control. If a material crosslinks prematurely, itmay not be possible for it to undergo further processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and others will be readily appreciated by theskilled artisan from the following description of illustrativeembodiments when read in conjunction with the accompanying drawings.

FIGS. 1A, 1B, and 1C are schematic drawings of a diblock copolymer anddomain structures it can form.

FIGS. 2A, 2B, and 2C are schematic drawings of a triblock copolymer anddomain structures it can form.

FIGS. 3A, 3B, and 3C are schematic drawings of a triblock copolymer anddomain structures it can form.

FIG. 4 is a schematic drawing that shows a novel new nanostructuredmaterial that includes ionically-conductive domains containing PEO andstructural domains that contain both PS and PXE, according to anembodiment of the invention.

FIG. 5 is a schematic drawing that shows a novel new nanostructuredmaterial that includes ionically-conductive domains containing PEO andstructural domains that contain both PS and PXE, according to anembodiment of the invention.

FIG. 6 is a schematic drawing that shows a novel new nanostructuredmaterial that includes ionically-conductive domains containing two kindsof polymers and structural domains that contain two kinds of polymers,according to an embodiment of the invention.

SUMMARY

In one embodiment of the invention, an electrolyte material isdisclosed. The electrolyte material has a first phase made of firstpolymers and a salt, such as a lithium salt. The first phase forms anionically-conductive domain in the electrolyte material. The electrolytematerial has a second phase made of second polymers third polymers. Thesecond phase forms a structural domain adjacent to theionically-conductive domain. The second phase may be cross-linked. Atleast some of the first polymers are covalently bonded to at least someof the second polymers to form first block copolymers. In onearrangement, at least some of the first polymers are covalently bondedto at least some of the third polymers to form second block copolymers.

In one arrangement, the second polymers and the third polymers are eachselected independently from the group consisting of polystyrene,hydrogenated polystyrene, polymethacrylate, poly (methyl methacrylate),polyvinylpyridine, polyvinylcyclohexane, polyimide, polyamide,polypropylene, poly (2,6-dimethyl-1,4-phenylene oxide) (PXE),polyolefins, poly (t-butyl vinyl ether), poly (cyclohexyl methacrylate),poly (cyclohexyl vinyl ether), poly (t-butyl vinyl ether), polyethylene,and polyvinylidene fluoride. In one arrangement, one or both of thesecond polymers and the third polymers has a first end group, and eachfirst end group is selected independently from the group consisting ofmethylacrylate, methyl (methacrylate), cyclic carbonate, anddimethylcarbmoyl.

In one arrangement, one or both of the second polymers and the thirdpolymers has a second end group opposite the first end group, and eachsecond end group is selected independently from the group consisting ofmethylacrylate, methyl (methacrylate), cyclic carbonate, anddimethylcarbmoyl.

The first polymer may be any of polyethers, polyamines, polyimides,polyamides, poly (alkyl carbonates), polynitriles, polysiloxanes,polyphosphazenes, polyolefins, polydienes, and combinations thereof. Thefirst polymer may be an ionically-conductive comb polymer with abackbone and pendant groups. The backbone may be one or more ofpolysiloxanes, polyphosphazenes, polyethers, polydienes, polyolefins,polyacrylates, polymethacrylates, and combinations thereof. The pendantsmay be one or more of oligoethers, substituted oligoethers, nitrilegroups, sulfones, thiols, polyethers, polyamines, polyimides,polyamides, poly (alkyl carbonates), polynitriles, other polar groups,and combinations thereof.

The ionically-conductive domain and the structural domain may bearranged as alternating lamellar domains. The ionically-conductivedomain and the structural domain may be arranged as bicontinuousdomains. The ionically-conductive domain and the structural domain mayalternate on a length scale of 5-500 nm.

The electrolyte material may also include fourth polymers in the firstphase. At least some of the fourth polymers may be covalently bonded toat least some of the third polymers to form third block copolymers. Thefourth polymers may be any of polyethers, polyamines, polyimides,polyamides, poly (alkyl carbonates), polynitriles, polysiloxanes,polyphosphazenes, polyolefins, polydienes, and combinations thereof.

In one arrangement, the electrolyte material has a modulus greater than1×10⁷ Pa at 80° C. In one arrangement, the electrolyte material has anionic conductivity greater than 10⁻⁴ Scm⁻¹ at 25° C. The electrolytematerial may be a solid at cell operating temperatures. The electrolytematerial may be a gel if a liquid electrolyte is added to it.

In one arrangement, lithium-ion conducting inorganic ceramics particlesare also included in the first phase of the electrolyte material. Theparticles may be made from one or more of Li₃N, LISICON, LIPON, LLTO,LLZO, LATP, thio-LISICON, Li₂S—P₂S₅, and garnet-type Li ion conductingoxides.

In another embodiment of the invention, an electrolyte material has anionically-conductive phase that includes PEO polymers and a salt. Theionically-conductive phase forms a first domain. The electrolytematerial also has a structural phase that includes PS polymers and PXEpolymers. The structural phase forms a second domain adjacent to thefirst domain. At least a portion of the PEO polymers and at least aportion of the PS polymers are covalently bonded together to form firstblock copolymers. The first block copolymers may be linear blockcopolymers. In one arrangement, at least a portion of the PEO polymersand a portion of the PXE polymers are covalently bonded together to formsecond block copolymers. The second block copolymers may be linear blockcopolymers. In one arrangement, at least a portion of the PS polymersand at least a portion of the PXE polymers are covalently bonded to oneanother.

In another embodiment of the invention, a battery electrode isdisclosed. The electrode has electrode active material particles,optional electronically-conductive particles, and an electrolytematerial as described above. The electrode active material particles andthe optional electronically-conductive particles are distributedrandomly throughout the electrolyte material.

If the electrode is a cathode, the electrode active material particlesmay be made of a material such as lithium iron phosphate (LFP), LiCoO2,LiMn2O4, lithium nickel cobalt aluminum oxide (NCA), and lithium nickelcobalt manganese oxide (NCM).

If the electrode is an anode, the electrode active material particlesmay be made of a material such as graphite, lithium metal, Li—Al, Li—Si,Li—Sn, Li—Mg, Si, Si—Sn, Si—Ni, Si—Cu, Si—Fe, Si—Co, Si—Mn, Si—Zn,Si—In, Si—Ag, Si—Ti, Si—Ge, Si—Bi, Si—Sb, Si—Cr, metal oxides, siliconcarbides, and mixtures thereof.

In another embodiment of the invention, a battery cell is disclosed. Thecell has a positive electrode comprising a positive electrode activematerial configured to absorb and release lithium ions, a negativeelectrode comprising a negative electrode active material configured toabsorb and release lithium ions, and an electrolyte material asdescribed above. The electrolyte material is positioned to provide ioniccommunication between the positive electrode and the negative electrode.

DETAILED DESCRIPTION

The preferred embodiments are illustrated in the context of blockcopolymer electrolytes in an electrochemical cell such as a battery. Theskilled artisan will readily appreciate, however, that the materials andmethods disclosed herein will have application in a number of othercontexts where high temperature operation is desirable.

Nanostructured Block Copolymer Electrolytes

A solid polymer electrolyte, when combined with an appropriate salt, ischemically and thermally stable and has an ionic conductivity of atleast 10⁻⁵ Scm⁻¹ at operating temperature. Examples of useful operatingtemperatures include room temperature (25° C.), 40° C., and 80° C. Inone arrangement, a polymer electrolyte has an ionic conductivity of atleast 10⁻³ Scm⁻¹ at battery cell operating temperatures, such as between20° C. and 100° C., or any range subsumed

therein. Examples of appropriate salts include, but are not limited to,metal salts selected from the group consisting of chlorides, bromides,sulfates, nitrates, sulfides, hydrides, nitrides, phosphides,sulfonamides, triflates, thiocynates, perchlorates, borates, orselenides of lithium, sodium, potassium, silver, barium, lead, calcium,ruthenium, tantalum, rhodium, iridium, cobalt, nickel, molybdenum,tungsten or vanadium. Examples of specific lithium salts include LiSCN,LiN(CN)₂, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃, Li(CF₃SO₂)₂N,Li(CF₃SO₂)₃C, LiN(SO₂C₂F₅)₂, lithium alkyl fluorophosphates, lithiumoxalatoborate, as well as other lithium bis(chelato)borates having fiveto seven membered rings, lithium bis(trifluoromethane sulfone imide)(LiTFSI), LiPF₃(C₂F₅)₃, LiPF₃(CF₃)₃, LiB(C₂O₄)₂, LiDFOB, and mixturesthereof. In other embodiments of the invention, for otherelectrochemistries, electrolytes are made by combining the polymers withvarious kinds of salts. Examples include, but are not limited toAgSO₃CF₃, NaSCN, NaSO₃CF₃, KTFSI, NaTFSI, Ba(TFSI)₂, Pb(TFSI)₂, andCa(TFSI)_(2.) As described in detail above, a block copolymerelectrolyte can be used in the embodiments of the invention.

FIG. 1A is a simplified illustration of an exemplary diblock polymermolecule 100 that has a first polymer block 110 and a second polymerblock 120 covalently bonded together. In one arrangement both the firstpolymer block 110 and the second polymer block 120 are linear polymerblocks. In another arrangement, either one or both polymer blocks 110,120 has a comb (or branched) structure. In one arrangement, neitherpolymer block is cross-linked. In another arrangement, one polymer blockis cross-linked. In yet another arrangement, both polymer blocks arecross-linked.

Multiple diblock polymer molecules 100 can arrange themselves to form afirst domain 115 of a first phase made of the first polymer blocks 110and a second domain 125 of a second phase made of the second polymerblocks 120, as shown in FIG. 1B. Diblock polymer molecules 100 canarrange themselves to form multiple repeat domains, thereby forming acontinuous nanostructured block copolymer material 140, as shown in FIG.1C. The sizes or widths of the domains can be adjusted by adjusting themolecular weights of each of the polymer blocks. In various embodiments,the domains can be lamellar, cylindrical, spherical, or gyroidaldepending on the nature of the two polymer blocks and their ratios inthe block copolymer.

In one arrangement the first polymer domain 115 is ionically conductive,and the second polymer domain 125 provides mechanical strength to thenanostructured block copolymer.

FIG. 2A is a simplified illustration of an exemplary triblock polymermolecule 200 that has a first polymer block 210 a, a second polymerblock 220, and a third polymer block 210 b that is the same as the firstpolymer block 210 a, all covalently bonded together. In one arrangementthe first polymer block 210 a, the second polymer block 220, and thethird copolymer block 210 b are linear polymer blocks. In anotherarrangement, either some or all polymer blocks 210 a, 220, 210 b have acomb structure. In one arrangement, no polymer block is cross-linked. Inanother arrangement, one polymer block is cross-linked. In yet anotherarrangement, two polymer blocks are cross-linked. In yet anotherarrangement, all polymer blocks are cross-linked.

Multiple triblock polymer molecules 200 can arrange themselves to form afirst domain 215 of a first phase made of the first polymer blocks 210a, a second domain 225 of a second phase made of the second polymerblocks 220, and a third domain 215 of a first phase made of the thirdpolymer blocks 210 b as shown in FIG. 2B. Triblock polymer molecules 200can arrange themselves to form multiple repeat domains 225, 215(containing both 215 a and 215 b), thereby forming a continuousnanostructured block copolymer material 240, as shown in FIG. 2C. Thesizes of the domains can be adjusted by adjusting the molecular weightsof each of the polymer blocks. In various arrangements, the domains canbe lamellar, cylindrical, spherical, gyroidal, or any of the otherwell-documented triblock copolymer morphologies depending on the natureof the polymer blocks and their ratios in the block copolymer.

In one arrangement the first and third polymer domains 215 are ionicallyconductive, and the second polymer domain 225 provides mechanicalstrength to the nanostructured block copolymer. In another arrangement,the second polymer domain 225 is ionically conductive, and the first andthird polymer domains 215 provide a structural framework.

FIG. 3A is a simplified illustration of another exemplary triblockpolymer molecule 300 that has a first polymer block 310, a secondpolymer block 320, and a third polymer block 330, different from eitherof the other two polymer blocks, all covalently bonded together. In onearrangement the first polymer block 310, the second polymer block 320,and the third copolymer block 330 are linear polymer blocks. In anotherarrangement, either some or all polymer blocks 310, 320, 330 have a comb(or branched) structure. In one arrangement, no polymer block iscross-linked. In another arrangement, one polymer block is cross-linked.In yet another arrangement, two polymer blocks are cross-linked. In yetanother arrangement, all polymer blocks are cross-linked.

Multiple triblock polymer molecules 300 can arrange themselves to form afirst domain 315 of a first phase made of the first polymer blocks 310a, a second domain 325 of a second phase made of the second polymerblocks 320, and a third domain 335 of a third phase made of the thirdpolymer blocks 330 as shown in FIG. 3B. Triblock polymer molecules 300can arrange themselves to form multiple repeat domains, thereby forminga continuous nanostructured block copolymer material 340, as shown inFIG. 3C. The sizes of the domains can be adjusted by adjusting themolecular weights of each of the polymer blocks. In variousarrangements, the domains can be lamellar, cylindrical, spherical,gyroidal, or any of the other well-documented triblock copolymermorphologies depending on the nature of the polymer blocks and theirratios in the block copolymer.

In one arrangement the first polymer domains 315 are ionicallyconductive, and the second polymer domains 325 provide mechanicalstrength to the nanostructured block copolymer. The third polymerdomains 335 provides an additional functionality that may improvemechanical strength, ionic conductivity, electrical conductivity,chemical or electrochemical stability, may make the material easier toprocess, or may provide some other desirable property to the blockcopolymer. In other arrangements, the individual domains can exchangeroles.

Choosing appropriate polymers for the block copolymers described aboveis important in order to achieve desired electrolyte properties. In oneembodiment, the conductive polymer: (1) exhibits ionic conductivity ofat least 10⁻⁵ Scm⁻¹ at electrochemical cell operating temperatures, suchas at 25° C. or at 80° C., when combined with an appropriate salt(s),such as lithium salt(s); (2) is chemically stable against such salt(s);and (3) is thermally stable at electrochemical cell operatingtemperatures. In another embodiment, the conductive polymer exhibitsionic conductivity of at least 10⁻³ Scm⁻¹ at electrochemical celloperating temperatures, such as at 25° C. or at 80° C., when combinedwith an appropriate salt(s). In one embodiment, the structural materialhas a modulus in excess of 1×10⁵ Pa at electrochemical cell operatingtemperatures. In one embodiment, the structural material has a modulusin excess of 1×10⁷ Pa at electrochemical cell operating temperatures. Inone embodiment, the structural material has a modulus in excess of 1×10⁹Pa at electrochemical cell operating temperatures. In one embodiment,the third polymer (1) is rubbery; and (2) has a glass transitiontemperature lower than operating and processing temperatures. It isuseful if all materials are mutually immiscible. In one embodiment theblock copolymer exhibits ionic conductivity of at least 10⁻⁴ Scm⁻¹ andhas a modulus in excess of 1×10⁷ Pa or 1×10⁸ Pa at electrochemical celloperating temperatures. Examples of cell operating temperatures include25° C. and 80° C.

In one embodiment of the invention, the conductive phase can be made ofa linear polymer. Conductive linear or branched polymers that can beused in the conductive phase include, but are not limited to,polyethers, polyamines, polyimides, polyamides, poly alkyl carbonates,polynitriles, and combinations thereof. The conductive linear orbranched polymers can also be used in combination with polysiloxanes,polyphosphazines, polyolefins, and/or polydienes to form the conductivephase.

In another exemplary embodiment, the conductive phase is made of comb(or branched) polymers that have a backbone and pendant groups.Backbones that can be used in these polymers include, but are notlimited to, polysiloxanes, polyphosphazines, polyethers, polydienes,polyolefins, polyacrylates, polymethacrylates (PMMA), and combinationsthereof. Pendants that can be used include, but are not limited to,oligoethers, substituted oligoethers, nitrile groups, sulfones, thiols,polyethers (PE), polyamines, polyimides, polyamides, alkyl carbonates,polynitriles, other polar groups, single ion conducting groups, andcombinations thereof.

Further details about polymers that can be used in the conductive phasecan be found in International Patent Application Number PCT/US09/045356,filed May 27, 2009, U.S. Pat. No. 8,691,928, issued Apr. 8, 2014,International Patent Application Number PCT/US10/21065, filed Jan. 14,2010, International Patent Application Number PCT/US10/21070, filed Jan.14, 2010, U.S. patent application Ser. No. 13/255,092, filed Sep. 6,2011, and U.S. Pat. No. 8,598,273, issued Dec. 3, 2013, all of which areincluded by reference herein.

There are no particular restrictions on the electrolyte salt that can beused in the block copolymer electrolytes. Any electrolyte salt thatincludes the ion identified as the most desirable charge carrier for theapplication can be used. It is especially useful to use electrolytesalts that have a large dissociation constant within the polymerelectrolyte. Although not always stated explicitly, it should beunderstood that all electrolyte materials disclosed herein also includean appropriate electrolyte salt(s).

Suitable examples include alkali metal salts, such as Li salts. Examplesof useful Li salts include, but are not limited to, LiPF₆, LiN(CF₃SO₂)₂,Li(CF₃SO₂)₃C, LiN(SO₂CF₂CF₃)₂, LiB(C₂O₄)₂, B₁₂F_(x)H_(12-x), B₁₂F₁₂, andmixtures thereof. Non-lithium salts such as salts of aluminum, sodium,and magnesium are examples of other salts that can be used with theircorresponding metals.

In one embodiment of the invention, single ion conductors can be usedwith electrolyte salts or instead of electrolyte salts. Examples oflithium single ion conductors include, but are not limited to, boundanions based on sulfonamide salts, boron-based salts, and sulfate salts.

It is especially useful if the structural phase is rigid and is in aglassy or crystalline state. In one embodiment of the invention, thestructural phase can be made of polymers such as polystyrene,hydrogenated polystyrene, polymethacrylate, poly (methyl methacrylate),polyvinylpyridine, polyvinylcyclohexane, polyimide, polyamide,polypropylene, poly (2,6-dimethyl-1,4-phenylene oxide) (PXE),polyolefins, poly (t-butyl vinyl ether), poly (cyclohexyl methacrylate),poly (cyclohexyl vinyl ether), poly (t-butyl vinyl ether), polyethylene,polyfluorocarbons such as polyvinylidene fluoride, or copolymers thatcontain styrene, methacrylates, and/or vinylpyridine. The structures ofthese polymers are shown below.

Any of these polymers may also have end groups. Each polymer may haveonly one (R or R′) end group or may have two (R and R′) end groups. Insome arrangements, a polymer has two end groups, R and R′, and R and R′are the same. In some arrangements, a polymer has two end groups, R andR′, and R and R′ are different. Groups that can be used as R and/or R′are shown below.

In one embodiment of the invention, the structural phase or domain of anelectrolyte material can be made up of a mixture of polymers. In somearrangements, at least a portion of the polymers are cross-linked orcovalently bonded together. Poly (2,6-dimethylphenylene oxide), alsoknown as poly (2,6-xylenyl oxide) or PXE, was developed in the 1950'sand 1960's as an engineering thermoplastic with good mechanicalproperties (tensile modulus=3.2-3.5 GPa), good chemical and electricalresistance, and a high glass transition temperature (Tg=210° C. at 2000Da molecular weight), allowing for its use over a wide temperaturerange. However, PXE is expensive to manufacture compared to mostcommodity polymers (e.g., polyacrylates, polystyrene (PS)). It wasdiscovered that PXE is fully miscible with PS, which is unusual, as manycombinations of different polymers cannot mix at a molecular level andcan form only crude physical blends. This discovery allowed mixtures ofPXE and PS to be marketed under the brand name Noryl™ (GE Plastics),wherein the PXE fraction provided good thermomechanical properties whilethe inclusion of PS allowed the manufacturing cost to be kept low.

In one embodiment of the invention, an electrolyte material 400 includestwo microscopically separated phases, an ionically-conductive phase 405and a structural phase 415, which are self-assembled into domains, asshown in FIG. 4. The ionically conductive phase 405 comprises poly(ethylene oxide) (PEO) 420 (or other suitable polymer, as discussedabove). The structural phase includes both polystyrene (PS) 460 as wellas PXE 440. The PXE 440 may

be thought of as an additive. Some or all of the PS polymers 460 arecovalently bonded to PEO polymers 420. The PXE polymers 440 are misciblewith the PS 460, and they both segregate to the structural phase 415 toseparate from the PEO 420. Other combinations of structural polymers arepossible, as long as they are miscible and can meet the modulus criteriadiscussed above. Thus, there are PEO-PS block copolymers 465, and thereare PXE polymers 440, which are not bonded to PEO 420, interspersed withthe PS polymers (or copolymer blocks) 460 within the structural phase415. This electrolyte material 400 may be referred to with the notation:PEO-PS(PXE). Although the schematic drawing in FIG. 4 shows a case wherethere are only two domains 405, 415, it should be understood that theremay be any number of repetitions of 405 and 415. In addition, althoughthis discussion has described materials based on PEO-PS diblockcopolymers, it should be understood that analogous materials can beformed from multiblock copolymers, such as PEO-PS-PEO triblocks becomingPEO-PS(PXE)-PEO or PS-PEO-PS triblocks becoming PS(PXE)-PEO-PS(PXE),within the embodiments of the invention.

In another embodiment of the invention, as shown in FIG. 5, anelectrolyte material 500 includes PEO 520, PS 560, and PXE 540. Anionically-conductive phase 505 is formed of poly (ethylene oxide) (PEO)520 (or other suitable polymer, as discussed above) and a structuralphase 515 is formed from a mixture of polymers such as PXE 540 andpolystyrene (PS) 560; at least some of the PEO 520 is covalently bondedto at least some of the PXE 540, and at least some of the PEO 520 iscovalently bonded to at least some of the PS 560. Some or all of the PEO520 may be covalently bonded. Suitable choice of polymer molecularweights and ratios results in the formation of nanostructured domainsmade up of ionically-conductive phases 505 and structural phases 515,which have been formed by self-assembly. The PXE 540 is miscible withthe PS 560, and they both segregate to the structural phase 515. Othercombinations of structural polymers are possible, as long as they aremiscible and can meet the modulus criteria discussed above. Thus, thereare PEO-PXE block copolymers 545 and PEO-PS block copolymers 565 withinthe electrolyte material 500. There may also be PXE polymers 540, whichare not bonded to PEO 520, and PS polymers 560, which are not bonded toPEO 520, interspersed within the structural domain or phase 515.Although the schematic drawing in FIG. 5 shows a case where there areonly two domains 505, 515, it should be understood that there may be anynumber of repetitions of 505 and 515. In addition, although thisdiscussion has been about formation of diblock copolymers, it should beunderstood that analogous multiblock copolymers, such as triblocks, arealso possible within the embodiments of the invention.

In another embodiment of the invention, an electrolyte material 600includes PEO 620, PS 660, PXE 640, and another polymer 680. Anionically-conductive phase 605 and a structural phase 615 have beenformed by self-assembly, as shown in FIG. 6. The ionically conductivephase 605 includes at least two different kinds of ionically-conductivepolymers that are miscible with one another. In an exemplary embodiment,one of the ionically-conductive polymers is poly (ethylene oxide) (PEO)620 and the other ionically-conductive polymer 680 is PMMA-g-PE(polymethacrylate grafted with polyether), which is miscible with PEO.Other suitable ionically-conductive polymers can be chosen from the listshown above. The structural phase includes a mixture of polymers such asPXE 640 and polystyrene (PS) 660. The PXE polymers 640 are miscible withPS 660, and they both segregate to the structural phase 615 whencombined with PEO 620 and PMMA-g-PE 680 to form the material 600. Othercombinations of structural polymers are possible, as long as they aremiscible and can meet the modulus criteria discussed above. In onearrangement, at least some PEO polymers 620 are covalently bonded to atleast some PS polymers 660. In one arrangement, at least some PEOpolymers 620 are covalently bonded to at least some PXE polymers 640. Inone arrangement, at least some PMMA-g-PE 680 are covalently bonded to atleast some PXE polymers 640. In one arrangement, at least some PMMA-g-PE680 are covalently bonded to at least some PS polymers 660. Thus, theremay be PEO-PS block copolymers 665 and PMMA-g-PE-PXE block copolymers647 within the material 600. There may also be (PMMA-g-PE)-PS blockcopolymers and PEO- PXE block copolymers (not shown) within theelectrolyte material 600.

There may also be PXE polymers 640 (not shown), which are not bonded ina block copolymer, and PS polymers 660, which are not bonded in a blockcopolymer, interspersed within the structural phase 615. Although theschematic drawing in FIG. 6 shows a case where there are only twodomains 605, 615, it should be understood that there may be any numberof repetitions of 605 and 615. In addition, although this discussion hasbeen about formation of diblock copolymers, it should be understood thatanalogous multiblock copolymers, such as triblocks, are also possiblewithin the embodiments of the invention.

Using a mixture of PXE and PS as an example, a PS(PXE) structural phasehas a glass transition temperature (T_(g)) that increases in a roughlylinear fashion as the proportion of PXE relative to PS increases, thatis, as more PXE is included. For example, using PXE with a T_(g) of 200°C., and PS with a T_(g) of 100° C., the T_(g) of a mixture of the two inthe structural phase would increase from about 100° C. at 0 wt % PXE inPS to about 150° C. at 50 wt % PXE in PS and to about 200° C. at 0 wt %PS in PXE. It may be useful to use PXE of sufficiently high molecularweights (≥2000 Da) to have high glass transition temperatures (≥200°C.). The modulus of a PEO-PS(PXE) material may be comparable to that ofthe PS-PEO block copolymer and is likely to be even greater. Such amixture of polymers in the structural phase of the inventive electrolytematerial can make it possible to operate a battery cell at highertemperature and with increased reliability and durability when used withlithium metal anodes in lithium batteries as compared to batteries usingPS-PEO alone.

In some embodiments of the invention, the ionically-conductive polymerhas a molecular weight greater than 50,000 Daltons or greater than100,000 Daltons. In some embodiments of the invention, the structuralpolymer has a molecular weight greater than 50,000 Daltons or greaterthan 100,000 Daltons. In some embodiments of the invention, diblockcopolymers that make up the electrolyte have molecular weights greaterthan 150,000 Daltons or greater than 350,000 Daltons. In someembodiments of the invention, triblock copolymers that make up theelectrolyte have molecular weights greater than 250,000 Daltons orgreater than 400,000 Daltons. The molecular weights given herein areweight-averaged molecular weights.

In another arrangement, crosslinking can be induced in the structuralphase, such as in the PS(PXE) phase, to further increase the modulus.

The sizes or dimensions of the domains in the electrolyte materialsdescribed herein can be adjusted by changing the relative amounts of theionically-conductive and structural phases. In various embodiments, thedomains can have morphologies that are lamellar, cylindrical, spherical,or bicontinuous, such as gyroidal. In one arrangement, theionically-conductive domain and the structural domain are arranged asalternating lamellar domains. In one arrangement, theionically-conductive domain and the structural domain are arranged asbicontinous domains. In one arrangement, wherein theionically-conductive domain and the structural domain alternate on alength scale of 5-500 nm, or any range subsumed therein. In onearrangement, structural lamellar domains have a width between 5 and 500nm, or any range subsumed therein. In one arrangement,ionically-conductive lamellar domains have a width between 5 and 500 nm,or any range subsumed therein.

It can be useful to optimize the molecular weight of PXE polymers usedin a PEO-(PS, PXE) block copolymer. Although high molecular weights(e.g., 2000 Da or greater) yield high glass transition temperatures(greater than 200° C.), processing of such high molecular weightpolymers can be difficult. Processing (especially solubility) generallybecomes easier with lower molecular weight. In an exemplary embodiment,the molecular weight of the PXE is lower than the molecular weight ofpolystyrene. This may be important for miscibility of PXE and PS in thenovel polymer materials disclosed herein. In one embodiment, themolecular weight of PXE in a PEO-PS(PXE) material is between 1000 and10,000 Daltons. In another embodiment, the molecular weight of PXE in aPEO-PS(PXE) material is between 1500 and 3000 Daltons.

In one arrangement, the PXE in PEO-PS(PXE) may be singly or doublyterminated with the phenolic groups as would normally be expected fromits industrial synthesis. In another arrangement, the PXE phenolic endscan be derivatized to form groups which are less likely to react withanodic or cathodic battery materials; for instance, alkylation of thephenolic groups to form alkyl ethers would reduce the likelihood ofreaction with a lithium metal anode. In another arrangement, the PXEphenolic ends can be derivatized to form groups with additionalfunctionality; for instance, allylation to form allyl ethers may allowthe PXE groups to be crosslinked through radical reactions.

In one arrangement, a PEO-PS(PXE) polymer mixture has between 0 wt % and90 wt % PXE and between 10 wt % and 100 wt % PS in the structural phase,or any range subsumed therein. In another arrangement, there is lessthan 50 wt % PXE and more than 50 wt % PS in the structural phase.

In one arrangement, the total volume fraction of the structural phase(PXE together with PS) within a PEO-PS(PXE) polymer mixture isapproximately 50%. The volume fraction of the conductive phase (PEO) isalso approximately 50%. Such a composition may favor formation oflamellar domains. In some arrangements, the structural phase makes upbetween 40 and 60 volume percent of the PEO-PS(PXE) material, and theconductive phase makes up the rest.

The ionic conductivity of the electrolyte materials disclosed herein canbe improved by including one or more additives in the ionicallyconductive phase. An additive can improve ionic conductivity by loweringthe degree of crystallinity, lowering the melting temperature, loweringthe glass transition temperature, increasing chain mobility, or anycombination of these. A high dielectric additive can aid dissociation ofthe salt, increasing the number of Li+ ions available for ion transport,and reducing the bulky Li+[salt] complexes. Additives that weaken theinteraction between Li+ and PEO chains/anions, thereby making it easierfor Li+ions to diffuse, may be included in the conductive phase. Theadditives that enhance ionic conductivity can be broadly classified inthe following categories: low molecular weight conductive polymers,ceramic particles, room temp ionic liquids (RTILs), high dielectricorganic plasticizers, and Lewis acids. In one arrangement, lithium-ionconducting ceramic particles are added to the ionically-conductivephase. Examples of useful, lithium-ion conducting inorganic ceramicsinclude sulfide, oxide and phosphate compounds. More specific examplesinclude Li₃N, LISICON (lithium super ionic conductor—e.g.,Li_(2+2x)Zn_(i-x)GeO₄), LIPON (lithium phosphorous oxy-nitride), LLTO(lithium lanthanide tantalum oxide), LLZO (lithium lanthanide zirconiumoxide), LATP (e.g., Li_(1.5)Al_(0.5)Ti_(1.5) (PO₄)₃), thio-LISICON(e.g., Li_(x)M_(1-y)M_(y)′S₄ (M=Si, Ge, and M′=P, Al, Zn, Ga, Sb)),Li₂S—P₂S₅, garnet-type Li ion conducting oxides, and the like.

Other additives can be used in the polymer electrolytes describedherein. For example, additives that help with overcharge protection,provide stable SEI (solid electrolyte interface) layers, and/or improveelectrochemical stability can be used. Such additives are well known topeople with ordinary skill in the art. Additives that make the polymerseasier to process, such as plasticizers, can also be used.

In one embodiment of the invention, neither small molecules norplasticizers are added to the block copolymer electrolyte and the blockcopolymer electrolyte is a dry polymer.

Further details about block copolymer electrolytes are described in U.S.Pat. No. 8,563,168, issued Oct. 22, 2013, U.S. Pat. No. 8,268,197,issued Sep. 18, 2012, and U.S. Pat. No. 8,889,301, issued Nov. 18, 2014,all of which are included by reference herein.

EXAMPLE

The following example provides details relating to composition,fabrication and performance characteristics of electrolyte materials inaccordance with the present invention. It should be understood thefollowing is representative only, and that the invention is not limitedby the detail set forth in this example.

A vial was charged with poly (2,6-dimethyl-1,4-phenylene oxide) (PXE,Aldrich 181781; see table), cyclohexanone (1.5 g) and xylenes (1.5 g),then stirred overnight at 45° C. To the resulting clear solutions wasadded PS-PEO-PS block copolymer (PEO 153 kDa, 58 wt %; 375 mg), and thesolutions were again stirred overnight at 45° C. These clear solutionswere then poured onto glass slides and heated on a 75° C. hotplate toprovide clear films. Samples of these films were analyzed by DSC todetermine glass transition temperature (Tg) and DMA to observe thesoftening point (storage modulus<10 MPa). These results are shown inTable I.

TABLE I PS-PEO- Sample PXE (mg) PS (mg) T_(g) (° C.) T_(soft) (° C.) A 0375 96 83 B 20 375 109 115 C 38 375 118 119 D 56 375 123 107 E 75 375127 138

In another embodiment of the invention, a battery electrode haselectrode active material particles, optional electronically-conductiveparticles, and an electrolyte material as described above. The electrodeactive material particles and the optional electronically-conductiveparticles are distributed randomly throughout the electrolyte material.

If the electrode is a cathode, the electrode active material particlesmay be made of a material such as lithium iron phosphate (LFP), LiCoO₂,LiMn₂O₄, lithium nickel cobalt aluminum oxide (NCA), and lithium nickelcobalt manganese oxide (NCM).

If the electrode is an anode, the electrode active material particlesmay be made of a material such as graphite, lithium metal, Li—Al, Li—Si,Li—Sn, Li—Mg, Si, Si—Sn, Si—Ni, Si—Cu, Si—Fe, Si—Co, Si—Mn, Si—Zn,Si—In, Si—Ag, Si—Ti, Si—Ge, Si—Bi, Si—Sb, Si—Cr, metal oxides, siliconcarbides, and mixtures thereof.

In another embodiment of the invention, a battery cell has a positiveelectrode comprising a positive electrode active material configured toabsorb and release lithium ions, a negative electrode comprising anegative electrode active material configured to absorb and releaselithium ions, and an electrolyte material as described above. Theelectrolyte material is positioned to provide ionic communicationbetween the positive electrode and the negative electrode.

This invention has been described herein in considerable detail toprovide those skilled in the art with information relevant to apply thenovel principles and to construct and use such specialized components asare required. However, it is to be understood that the invention can becarried out by different equipment, materials and devices, and thatvarious modifications, both as to the equipment and operatingprocedures, can be accomplished without departing from the scope of theinvention itself

We claim:
 1. An electrolyte material comprising: a first phasecomprising a plurality of first polymers and a salt, the first phaseforming an ionically-conductive domain; and a second phase comprising aplurality of second polymers and third polymers, the second phaseforming a structural domain adjacent to the ionically-conductive domain;wherein at least some of the first polymers are covalently bonded to atleast some of the second polymers to form first block copolymers;wherein the second polymers and the third polymers are each selectedindependently from the group consisting of polystyrene, hydrogenatedpolystyrene, polymethacrylate, poly (methyl methacrylate),polyvinylpyridine, polyvinylcyclohexane, polyimide, polyamide,polypropylene, poly (2,6-dimethyl-1,4-phenylene oxide) (PXE),polyolefins, poly (t-butyl vinyl ether), poly (cyclohexyl methacrylate),poly (cyclohexyl vinyl ether), poly (t-butyl vinyl ether), polyethylene,and polyvinylidene fluoride; and wherein one or both of the secondpolymers and the third polymers further comprises a first end group, andeach first end group is selected independently from the group consistingof methylacrylate, methyl (methacrylate), cyclic carbonate, anddimethylcarbmoyl.
 2. The electrolyte material of claim 1 wherein one orboth of the second polymers and the third polymers further comprises asecond end group opposite the first end group, and each second end groupis selected independently from the group consisting of methylacrylate,methyl (methacrylate), cyclic carbonate, and dimethylcarbmoyl.
 3. Theelectrolyte material of claim 1 wherein at least some of the firstpolymers are covalently bonded to at least some of the third polymers toform second block copolymers.
 4. The electrolyte material of claim 1wherein the first polymer is selected from the group consisting ofpolyethers, polyamines, polyimides, polyamides, poly (alkyl carbonates),polynitriles, polysiloxanes, polyphosphazenes, polyolefins, polydienes,and combinations thereof.
 5. The electrolyte material of claim 1 whereinthe first polymer comprises an ionically-conductive comb polymer, thecomb polymer comprising a backbone and pendant groups.
 6. Theelectrolyte material of claim 5 wherein the backbone comprises one ormore selected from the group consisting of polysiloxanes,polyphosphazenes, polyethers, polydienes, polyolefins, polyacrylates,polymethacrylates, and combinations thereof.
 7. The electrolyte materialof claim 5 wherein the pendants comprise one or more selected from thegroup consisting of oligoethers, substituted oligoethers, nitrilegroups, sulfones, thiols, polyethers, polyamines, polyimides,polyamides, poly (alkyl carbonates), polynitriles, other polar groups,and combinations thereof.
 8. The electrolyte material of claim 1 whereinthe ionically-conductive domain and the structural domain are arrangedas alternating lamellar domains.
 9. The electrolyte material of claim 8wherein the ionically-conductive domain and the structural domain eachhas a width between 5 and 500 nm.
 10. The electrolyte material of claim1 further comprising fourth polymers in the first phase wherein at leastsome of the fourth polymers are covalently bonded to at least some ofthe third polymers to form third block copolymers.
 11. The electrolytematerial of claim 10 wherein the fourth polymers are selected from thegroup consisting of polyethers, polyamines, polyimides, polyamides, poly(alkyl carbonates), polynitriles, polysiloxanes, polyphosphazenes,polyolefins, polydienes, and combinations thereof.
 12. The electrolytematerial of claim 1 wherein the salt is a lithium salt.
 13. Theelectrolyte material of claim 1 wherein the electrolyte material is asolid at temperatures between 20° C. and 100° C.
 14. The electrolytematerial of claim 1 further comprising a liquid electrolyte, wherein theelectrolyte material is a gel.
 15. The electrolyte material of claim 1further comprising lithium-ion conducting inorganic ceramics particlesin the first phase.
 16. The electrolyte material of claim 1 wherein thesecond phase is cross-linked.
 17. A battery electrode, comprising:electrode active material particles; an electrolyte material accordingto claim 1 or claim 2; and optional electronically-conductive particles;wherein the electrode active material particles and the optionalelectronically-conductive particles are distributed randomly throughoutthe electrolyte material.
 18. The electrode of claim 17 wherein theelectrode is a cathode, and the electrode active material particlescomprise a material selected from the group consisting of lithium ironphosphate (LFP), LiCoO₂, LiMn₂O₄, lithium nickel cobalt aluminum oxide(NCA), and lithium nickel cobalt manganese oxide (NCM).
 19. Theelectrode of claim 17 wherein the electrode is an anode, and theelectrode active material is selected from the group consisting ofgraphite, lithium metal, Li—Al, Li—Si, Li—Sn, Li—Mg, Si, Si—Sn, Si—Ni,Si—Cu, Si—Fe, Si—Co, Si—Mn, Si—Zn, Si—In, Si—Ag, Si—Ti, Si—Ge, Si—Bi,Si—Sb, Si—Cr, metal oxides, silicon carbides, and mixtures thereof.